Data visualization

Data visualization is showing data as pictures, like charts, maps and heat maps, so the eye can see patterns, comparisons and outliers that a table hides.

Select any words here to ask your Maestro about them.

A chart draws each store as a circle and makes it twice as wide when sales double. South sold twice what North did. By area, how many times bigger is South's circle than North's?

Three stores in a chain. Example data.

Why it works: the eye spots a long bar, a rising line or an odd outlier faster than it reads a column of numbers. That speed cuts both ways: a picture can mislead just as fast.

How to choose: by the question. To compare, a bar chart; over time, a line chart; for a relationship, a scatter plot; to cross two categories, a heat map. A dashboard puts several together.

Where it breaks: when the picture says something the numbers don't: a cut axis, a color scale stretched by one extreme value, a shape scaled the wrong way.

How it's used

Pick by the question

Which chart for which question

marked: Which store sold most in October? Bars for the three storesBars start at zero and compare by length, which the eye reads well.
How did North do month by month? A line chart
Do stores that spend more on ads sell more? A scatter plot
How big is a typical ticket at North? A histogram

Start from the question, then pick the chart; last, check that the eye reads the number the way you meant.

When to look closer

Two axes on one chart

Revenue and ad spend

marked: Left axis: revenue. Right axis: ad spend. The lines cross in March

Revenue (left axis) and ad spend (right axis) cross in March. About what share of March revenue is ad spend?

Ask your Maestro about Data visualization

It answers from the free course page closest to this word, the way it answers while you study.

Example

You: What does "Data visualization" mean, in plain words?

Your Maestro: I'll explain it with a case of yours: it sticks better than a definition. Which number at work would make more sense as a chart?

Asking about: Answers from the page "When to use a bar chart? Sort the bars to compare"

Only this browser keeps what you ask here. How it works

Learn more

Data and information visualization (Wikipedia)

Bar chart
A bar chart compares amounts across categories: each bar is a category and its length is the number. Use it to see which branch sold the most.
Line chart
A line chart joins points in order, almost always over time, to show how a number changes: whether it rises, falls or repeats every season.
Scatter plot
A scatter plot draws one dot per case, with one variable on each axis, to show whether two numbers move together: when one goes up, does the other go up, go down, or do nothing?
Histogram
A histogram shows how the values in a column of numbers are spread out: it cuts them into ranges of equal width and draws one bar per range, as tall as the number of values that fall in it.

The whole glossary